Oxyfluoride compounds for lithium-cells and batteries

Abstract

The present invention concerns specific new compounds of formula Li.sub.(2x)Na.sub.(x)MO.sub.(2y/2)F.sub.(1+y) (where 0x0.2 and 0.6y0,8 and M is a transition metal), cathode material comprising the new compounds, batteries and lithium-cells comprising said new compound or cathode material, a process for the production of the new compound and their use.

Claims

1. A compound of formula Li.sub.(2x)Na.sub.xMO.sub.(2y/2)F.sub.(1+y), wherein M represents one or more of V, Mo, Cr, and W and 0x0.2 and 0.6<y<0.8.

2. The compound of claim 1, wherein x =0 and/or y =0.

3. The compound of claim 1, wherein x =0.1 and/or y =0.

4. The compound of claim 1, wherein M is in a trivalent oxidation state.

5. The compound of claim 1, wherein M represents V.

6. The compound of claim 1, wherein M represents Cr.

7. The compound of claim 2, wherein M represents V in a trivalent oxidation state.

8. The compound of claim 2, wherein M represents Cr in a trivalent oxidation state.

9. The compound of claim 3, wherein M represents V in a trivalent oxidation state.

10. The compound of claim 3, wherein M represents Cr in a trivalent oxidation state.

11. The compound of claim 2, wherein M represents one or more of V, Mo, Cr, W in a trivalent oxidation state.

12. The compound of claim 3, wherein M represents one or more of V, Mo, Cr, W in a trivalent oxidation state.

13. A cathode material, wherein the material comprises the compound of claim 1.

14. The cathode material of claim 13, wherein the material further comprises carbon black.

15. A battery and/or lithium cell which comprises the compound of claim 1.

16. The battery or lithium cell of claim 15, wherein the battery or lithium cell has a specific capacity of 150-500 mAh/g and/or an energy density of from 300 to 1,200 Wh/kg.

17. The battery or lithium cell of claim 15, wherein the battery or lithium cell further comprises a counter electrode comprising or consisting of lithium.

18. A process for the production of the compound of claim 1, wherein the process comprises milling inorganic precursors of the compound.

19. The process of claim 2, wherein the inorganic precursors are milled mechanically.

20. The compound of claim 2, wherein x =0 and y =0.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 Powder X-ray diffraction patterns of synthesized Li.sub.2VO.sub.2F after ball-milling and mixture of starting precursors according to Example 1.

(2) FIG. 2 Electrochemical charge/discharge voltage versus time for Li.sub.2VO.sub.2F using lithium as counter electrode measured between 4.1 and 1.3 V at a current rate of 7.7 mA/g at 40 C. according to Example 1.

(3) FIG. 3 Electrochemical charge/discharge voltage versus time for Li.sub.(1.9)Na.sub.(0.1)VO.sub.2F using lithium as counter electrode measured between 4.0 and 1.3 V at a current rate of 7.23 mA/g at 25 C. according to Example 2.

(4) FIG. 4 Electrochemical charge/discharge voltage versus time for Li.sub.2CrO.sub.2F using lithium as counter electrode measured between 4.7 and 1.3 V at a current rate of 15.4 mAg.sup.1 at 40 C. according to Example 4. The initial discharge capacity was 340 mAhg.sup.1.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

EXAMPLES

Example 1

(5) 0.5188 g LiF, 0.298 8 g Li.sub.2O and 1.499 g V.sub.2O.sub.3 powders were mixed together, placed in a gas-tight container in an argon-filled glovebox and subsequently ball-milled at 450 rpm for 50 h to obtain Li.sub.2VO.sub.2F.

(6) FIG. 1 shows the X-ray diffraction patterns for the starting mixture and ball-milled Li.sub.2VO.sub.2F. The sharp diffraction peaks from the starting precursors disappeared and new phase with broad diffraction peaks were formed after ball-milling. The crystallite size is about 9 nm, calculated by Scherrer equation.

(7) As-obtained Li.sub.2VO.sub.2F powders were mixed with carbon black (4:1 w/w) by ball-milling at 200 rpm for 5 h.

(8) Electrochemical tests were performed using a Swagelok-type half-cell setup using lithium as counter electrode, two sheets of glass fiber as separator and 0.7 M lithium bis(oxalato)borate in ethylene carbonate/diethyl carbonate (7:8 w/w) as electrolyte.

(9) FIG. 2 shows the galvanostatic charge/discharge performance tested between 1.3 and 4.1 V versus lithium at a current rate of 7.7 mA g at 40 C. The initial discharge capacity was 400 mAh g1.

(10) Li.sub.2VO.sub.2F shows excellent performance over further cycling.

Example 2

(11) 0.4928 g LiF, 0.2838 g Li.sub.2O, 0.0420 g NaF, 0.0530 g Na.sub.2CO.sub.3 and 1.499 g V.sub.2O.sub.3 powders were mixed together, placed in a gas-tight container in an argon-filled glovebox and subsequently ball-milled at 450 rpm for 24 h to obtain Li.sub.(1.9)Na.sub.(0.1)VO.sub.2F.

(12) As-obtained Li.sub.(1.9)Na.sub.(0.1)VO.sub.2F powders were mixed with carbon black (4:1 w/w) by hand-grinding. Eletrochemical tests were performed using the similar procedure as described in Example 1.

(13) FIG. 3 shows the galvanostatical charge/discharge performance tested between 1.3 and 4.0 V versus lithium at a current rate of 7.23 mA/g at 25 C.

(14) The initial discharge capacity was 290 mAh g1. Li.sub.(1.9)Na.sub.(0.1)VO.sub.2F shows excellent cycling stability over further cycling.

Example 3

(15) 0.9805 g LiF, 0.06 125 g Li.sub.2O and 1.499 g V.sub.2O.sub.3 powders were mixed together, placed in a gas-tight container in an argon-filled glovebox and subsequently ball-milled at 450 rpm for 20 h to obtain Li.sub.2VO.sub.(1.6)F.sub.(1.8). As-obtained Li.sub.2VO.sub.(1.6)F.sub.(1.8) powders were mixed with carbon black (4:1 w/w) by ball-milling at 250 rpm for 4 h. Electrochemical tests were performed using the similar procedure as described in Example 1.

(16) Galvanostatic charge/discharge was performed between 4.1 and .1.3 V versus lithium at a current rate of 7.17 mA/g at 40 C. The initial discharge capacity was 170 mAh/g.

Example 4

(17) 0.219 g LiF, 0.139 g Li.sub.2O and 0.642 g Cr2O.sub.3 powders were mixed together, placed in a gas-tight container in an argon-filled glovebox and subsequently ball-milled at 450 rpm for 30 h to obtain Li.sub.2CrO.sub.2F. As-obtained Li.sub.2CrO.sub.2F powders were mixed with carbon black (7:3 w/w) by ball-milling at 400 rpm for 10 h. Electrochemical tests were performed using a Swagelok-type half-cell setup using lithium as counter electrode, two sheets of glass fiber as separator and 1.0 M LiPF.sub.6 in ethylene carbonate/dimethyl carbonate (1:1 v/v) as electrolyte.